Question

A car, moving with a speed of 50 km/hr, can be stopped by brakes after at least 6m. If the same car is moving at a speed of 100 km/hr, the minimum stopping distance is

• A. 6m
• B. 12m
• C. 18m
• D. 24m

Answer 1

Answer: (D)

24m

Answer 2

$v^{2} = u^{2} - 2as$ ⇒ $0 = u^{2} - 2as$⇒ $s = \frac{u^{2}}{2a} \Rightarrow s \propto u^{2}$

(As a = constant)

$\frac{s_{2}}{s_{1}} = \left( \frac{u_{2}}{u_{1}} \right)^{2} = \left( \frac{100}{50} \right)^{2} \Rightarrow s_{2} = 4s_{1} = 4 \times 12 = 24m.$